Precoding with Known Transmit Coupling and Spatial Covariance Matrices

A closed-form precoding scheme using the knowledge of transmit coupling and spatial covariance matrices is proposed, which ensures that the achievable rate increases with the number of transmit antennas when the size of the transmit antenna array is fixed and the radiated power, but not the amplifier output power, is constrained. Eigenvalue-proportional power allocation is employed in this precoding scheme. Simulation shows that the performance of eigenvalue-proportional power allocation is close to that of covariance matrix based waterfilling power allocation. Energy efficiency of different schemes is evaluated and compared.